JPS6120480B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an earth sensor mounted on a flying object, such as a three-axis attitude control satellite, and used to detect attitude errors, and more particularly to an improvement in an earth presence detector.

Figure 1 shows a conventional earth sensor.
is a substrate on which a thermal infrared image (hereinafter referred to as the earth image) of the earth (not shown) is formed. A plurality of thermal infrared detectors 12, 13 to 19 are arranged at the periphery of the base 11 to detect images of the earth. The light receiving areas of these thermal infrared detectors 12, 13 to 19 are all equal, and the thermal infrared detectors 12, 13 to 19
The diameter of the circle formed by is approximately equal to the diameter of the earth image formed on the base 11.
Therefore, these thermal infrared detectors 12, 13-
If the satellite is operated so that the signals outputted from 19 are all equal, the satellite can be maintained in a normal attitude.

On the other hand, a plurality of thermal infrared detectors 1 are mounted on the base 11.
An earth presence detector 20 that outputs an earth presence detection signal (hereinafter referred to as an earth presence signal) is provided at the center of the earth presence detection signals 2, 13 to 19. Before the attitude control of the satellite, the presence of the earth is first detected. That is, when the earth is not within the field of view of the earth sensor, the satellite is operated greatly and the earth presence detector 20 detects the earth. Then, when the earth is detected by the earth presence detector 20 and an earth presence signal is output, it is determined that the earth has been detected. Thereafter, after the satellite is further operated and the earth image is completely captured by the earth sensor, the above-mentioned thermal infrared detector 12,
13 to 19, the attitude of the satellite is maintained.

By the way, the earth presence detector 20 is adapted to output an earth presence signal when energy exceeding a set threshold is incident thereon.
Therefore, when the incident energy is large, for example, even when the sun comes within the field of view, there is a possibility that an earth presence signal will be output, which poses a serious problem in controlling the attitude of the satellite.

This invention has been made based on the above circumstances, and its purpose is to provide an earth sensor that does not erroneously detect the presence of the earth.

An embodiment of the present invention will be described below with reference to the drawings. Note that the same parts in FIG. 2 as in FIG. 1 are given the same reference numerals.

In FIG. 2, a base body 11 is provided with thermal infrared detectors 12, 13 to 19 for detecting an earth image along the circumference of the earth image formed on the base body 11, and these thermal infrared detectors constitute A plurality of earth presence detectors 21, 22, 23, and 24 are provided in the center of the circle. This earth existence detector 21, 22, 23,
24 is a detector for detecting an image of the earth like the thermal infrared detectors 12, 13 to 19, and the distance l between these is the diameter of the image of the sun within the field of view of the earth sensor, that is, the diameter of the image of the sun on the base 11. It is said to be larger than the diameter of the image of the sun to be formed (hereinafter referred to as the solar image).
The diameter of the earth image and sun image on this base 11 is
Although it differs depending on the type of lens (not shown) that guides the image of the Earth onto 1, there is generally a relationship between the diameter of the solar image and the diameter of the Earth.

In the above configuration, the thermal infrared detectors 12, 13
to 19, the satellite is operated so that the earth image is detected as in the conventional case, and the output signals of the thermal infrared detectors 12, 13 to 19 are equal, and the attitude of the satellite is maintained correctly.

On the other hand, when detecting the presence of the Earth before the attitude control described above, the Earth sensor first detects the presence of the Earth, but if the Earth is within the field of view of the Earth sensor, the above thermal infrared Attitude control is performed by the devices 12, 13-19. However, if the earth is not within the field of view of the earth sensor, the satellite will be operated significantly and at least two of the earth presence detectors 21, 22, 23, 24 will be
When the earth image is within the field of view of each detector, an earth presence signal is output, and it is determined that the earth has been detected.

FIG. 3 shows this circuit configuration. The output signals (output voltages) of the earth presence detectors 21, 22, 23, and 24 are sent to comparators 31, 32, and 3, respectively.
3 and 34, and this comparator 3
A predetermined threshold signal Vt is supplied to the other input terminals of the input terminals 1, 32, 33, and 34, respectively. This comparator 3
For example, the output signals of 1, 32, 33, and 34 are output from two adjacent AND circuits 41, 42, 43, and 4 that are the same.
The output signals of the AND circuits 41, 42, 43, and 44 are respectively supplied to the OR circuit 45.

With the above configuration, the earth image is detected by the earth presence detector 2.
When it comes within the field of view of two adjacent Earth presence detectors among 1, 22, 23, and 24, and the output signals of both Earth presence detectors exceed the threshold signal Vt, the The output signal satisfies the input conditions of the AND circuit, and the AND circuit outputs the signal. This signal is supplied to the OR circuit 45, and the OR circuit 45 outputs a ground presence signal.

In addition, earth presence detectors 21, 22, 23, 24
When the sun enters the field of view of one of the earth presence detectors, a signal is output from that earth presence detector, but the input conditions of the AND circuit to which this signal is supplied are not satisfied. Furthermore, since the distance l between the earth presence detectors 21, 22, 23, and 24 is made larger than the diameter of the solar image, the sun will not enter the field of view of adjacent earth presence detectors at the same time. Therefore, the earth presence detector 21,2
Even if any one of the sensors 2, 23, and 24 detects the sun, the earth presence signal will not be erroneously output, and the earth can be detected reliably.

In the above embodiment, the presence of the earth was detected using adjacent earth presence detectors, but the present invention is not limited to this, and the point is that the presence of the earth can be detected using the output signals of two or more earth presence detectors. The number of earth presence detectors and the configuration of the circuit for generating the earth presence signal can be changed as appropriate.

It goes without saying that various other modifications can be made without departing from the gist of the invention.

As described in detail above, according to the present invention, it is possible to provide an earth sensor that does not erroneously detect the presence of the earth.

[Brief explanation of the drawing]

FIG. 1 is a diagram shown to explain the configuration of a thermal infrared detector and an earth presence detector applied to a conventional earth sensor, and FIGS. 2 and 3 are examples of the earth sensor according to the present invention, respectively. 2 is a diagram showing the configuration of the earth presence detector, and FIG. 3 is a circuit diagram for generating an earth presence signal. 12-19... Thermal infrared detector, 21-24... Earth presence detector, 31-34... Comparator, 41-44
...AND circuit, 45...OR circuit.

Claims (1)

[Claims] 1. A base body mounted on a flying object on which an earth image and a sun image are formed, and a plurality of earth images arranged on this base body at predetermined intervals along the circumference of the formed earth image. a thermal infrared detector that detects the presence of the earth, a plurality of earth presence detectors arranged in the center of the thermal infrared detector at a distance larger than the diameter of the imaged solar image; A comparator that compares the output signal from the detector with a predetermined threshold signal and a predetermined threshold signal, and output ends of the comparators corresponding to adjacent earth presence detectors of the plurality of earth presence detectors are connected, respectively. An earth sensor comprising a plurality of AND circuits, and an OR circuit in which the output ends of the plurality of AND circuits are connected to each other.